Electronic structure of fcc Th: Spin-orbit calculation with 6 p 1'2 local orbital extension

Ab initio electronic structure calculations of actinide compounds have a weak point when the spin-orbit coupling is treated using a scalar-relativistic basis and the second variational method due to the poor description of the $6p$ states. We extend the basis set of the second variational step by including relativistic ${p}_{1/2}$ local orbitals for the description of the $6p$ states. Our results show that the additional ${p}_{1/2}$ local orbitals significantly improve the description of actinides.